Python script - objects are grey after export to glb file
glTF (GLB) uses a PBR material system, and the Blender exporter requires the exported materials to use the &quot;Principled BSDF&quot; node.  The glTF material system is documented in the Blender Manual.
If the blender_osm addon is producing materials based on the Diffuse node or similar, these won't export correctly in the current version of the glTF exporter.  Your script will need to convert these materials to use Principled BSDF.